Process of obtaining soluble potassium compounds in the manufacture



Patented May 1, 1923.

UNITED STATES PRQOIESS GI QB'ITAINING Sl'lllIlUB N0 Drawing. Application filed December To all whom it may concern:

Be it known that l, llnnoruuou i l. Human, a citizen ot the United States, residing at Riverside, in the county of Riverside and State of (lalilbrnia, have invented. certain new and useful Improvements in llrocesser-i oil? Obtaining Soluble Potassium Compounds in the lrlamrlacture of Cement, of which the tlollowing is a specification.

The present invention relates to the pro duction and recovery of soluble potassium (:orn )ou11cls in. the manufacture of Portland cement from potassiterous materials, the object of the invention being to recover as large a proportion as pos, 'l

rile oi the potas sium compounds contained in the cement raw mix, in a water-soluble condition, in which they are readily salable.

The production oi POllltSSllllTl compounds by the collection and subsequent treatment; of flue dust obtained in the manufacture of Portland cement has already been investigated to some extent and a number oi? patents have been taken out by various inventors, looking to this end. Portland cement is ordinarily made from materials containing more or less potassium, the potassium compounds being usually in an insoluble condition in the raw mix. In the calcination and clinhering, of the cementernahing raw materials, a considerable amount of the potas sium compounc s contained therein is driven oil by the heat, and apart oi? these compounds are collected with the flue dust.

Experiments have clearly demonstrated that the potassium compounds as yolatilieed by heating the materials, for example in a coal-fired rotary kiln, at the time of their liberation, are substantially entirely in a water-soluble state. These compounds however, do not entirely remain in a water-sold hle condition in the collected flue dust. llt appears possible that the soluble potassium compounds may react more or less with the coal ash present in the kiln gases, and produce compounds thereby which are not readily soluble, thereby losing a part, and in some instances a very large part oi the soluble potassirun compounds. In ordinary practice the kiln is fired by a blast of coal dust introduced at the lower end of the kiln, with a blast of air, thereby producing a name which travels upwardly through the lulu; rotary IENT.

15, 191?. la'crial No. 20136".

hilu being employed. The tendency of the ash our the coal dust is accordingly to trai cl toward the stack, and the potassium coinpruulds being rolatilir/zed and traveling in the same direction, are brought into more or less intimate contact w th the coal ash, and erha gxs by reaction between these to mate rials a silicious, more or less glassy mass is produced, in a finely divided state. This product of reaction of the coal ash and potasslum compounds settles out with the line dust, and is not readily amenable to treatment with either hot or cold water.

l have found by experimentation that if the cement flue dust, containing insoluble potassium conipormds (either before or after leaching with water) be mixed with an amount of carbon, for example coal dust, substantially equal in weight to the lK U content of the line dust, and also be mixed with calcareous material, for example lime or chalk, l

in such proportions as to produce a ure having a Cat) Sit); ratio 0']? about and preferably not less than 2:1, a mass is produced which by heating, for example in a rotary kiln, to a temperature between 600 i000 (l, iroduces a product in which substantially the entire content of potassium compounds is rendered water-soluble, and can be separated by leaching with water.

The CaUtSiU ratio is preferably about That is to say the amount of calcium present (existing as lime or other calcium compound) is such as to furnish two nucle- M, i of Call for each molecule of silica present (GTlIlStlllg either as such or in the :l oriu o'l silicates, etc).

'lo this end, the fine dust collected by any of the orejlinary methods, for example by cy clone dust separators, electrical precipita tiou, cooli nd settling]; by greatly reducion the ropeed oil? the :tlue eases, or by a wet treatment oil the line gases, or other method, is minted with coal and lime (or other can liruiaceous and calcareous materials) the amount of coal added being); at least equal and usmtlly slightly more than) the weight of the total M 0 content of the flue dust. This mass is then transferred to a kiln or furnace and heated to a temperature of 600-l000 U The heating may be ,ctively carried out in a rotary kiln, and hould he to a temperature below that it which any very considerable amount of the potassium compounds would be fumed off. The furnaced mass is then leached with water, hot water being preferred, and the solution separated from the insoluble matter, and the solution subsequently evaporated to recover the potassium compounds.

The flue dust as originally obtained may contain considerable calcareous material, or may contain considerable finely divided. carbon, and the content of these materials may of course be taken into consideration in determining the amounts of carbon and lime to be added to the flue dust in producing the mixture to be heated. It is accordingly obvious'that if either or both the lime and carbon are suflicient, it is not necessary to add further quantities.

p The original flue dust, before mixing with lime and coal or the like, may be leached with water to remove soluble potassium compounds, it so desired. This treatment leaves a Wet mass of flue dust which may be ground with the lime and coal either in a wet state or after drying.

What I claim is:

1. A process of producing wat r-soluble potassium salts which comprises burning a potassiferous cement-making raw mix, and collecting flue dust containing potassium compounds not readily soluble in water, producing therefrom a mixture containing such not-readilysoluble-potassium compounds, and calcareous material having a CaO :SiO ratio of not less than 2:1, and containing carbonaceous material of a reducing character, at least about equal in amount to the K 0 content, and heating the mixture, to a temperature of at least 600 C., but below the temperature at which any large part of the potassium compounds would be volatilized, and thereafter extracting the readily soluble potassium compounds therefrom.

2. A'process of producing water-soluble potassium compounds from cement kiln fine dust and like material which comprises producing a mixture containing such dust, calcareous material and carbonaceous material of a reducing character, the mixture containing a molecular ratio of CaOzSiO equal to about 2:1, and containing a can bonaceous reducing agent at least equal to the weight of actual K 0 present, heating such dust to a temperature of about 600 to i000 (1., under reducing conditions and thereafter leaching the heated mass with water.

3. A process which comprises heating a pulverulent mixture containing cement fine dust, calcareous material and carbonaceous material of a reducing character, the mixture containing a molecular ratio of (la():Si() equal to about 2:1, and containing a carbonaceous reducing a ent at least equal to the weight ot actual h t) present to at least a red heat, but below that at which large quantities of the potassium content thereof would be lost by vaporization, while maintaining the heated material under reducing conditions, and thereafter leaching the same.

4.. A process which comprises burning potassiferous cement-forming material by a flame o1" fine coal. collecting the flue dust, and producing a mixture of at least that portion of such dust in which the potassium content is not readily water-soluble, with calcareous material and carbonaceous material, said mixture having a CaO:Si() ratio of not less than about 2:1, and containing at least as much free carbon as K 0 by weight, burning such mixture at not below redness but below the temperature at which a substantial part of the potassium compounds would be volatilized, and removing the water-soluble potassium compounds therefrom.

A process which comprises heating a mixture containing potassiferous cement flue dust, calcareous material and carlxmaceous material of a reducing character, such latter being present in amount at least substantially equal to the K 0 content of the dust. and such heating bein to a tem erak b ture corresponding to at least a red heat. but below that at which large quantities of the potash content of the dust would be lost by vaporization, and thereafter leaching the same.

In testimony whereof I aflix my signature.

FREDERICK W. HUBER. 

